Logarithmic periodic antenna



Sept. 27, 1966 L ET AL 3,276,027

LOGARITHMIC PERIODIC ANTENNA Filed Aug. '7, 1962 2 Sheets-Sheet 1 II II II II II II II II II II II II II I] TI ll "1] II II II II II II ll I NN 7N lNVENTORS ROSS L. BELL WILLIAM L.WERNER BY fad/6. M ATTORNEY Sept. 27, 1966 L, BELL ET AL 3,276,027

LOGARITHMIC PERIODIC ANTENNA Filed Aug. '7, 1962 2 Sheets-Sheet 2 HI N 2 mm 5 WWW] Hg INVENTORS R L. BELL W L AM L.WERNER ATTORNEY United States Patent 3,276,027 LOGARITHMIC PERIODIC ANTENNA Ross L. Bell, Dallas, Tex., and William L. Werner, Sunnyvale, Calif., assignors to Granger Associates, Palo Alto, Calif., a corporation of California Filed Aug. 7, 1962, Ser. No. 215,339 2 Claims. (Cl. 343-7925) This invention relates generally to logarithmic periodic antennas and the invention relates more particularly to a novel logarithmic periodic antenna having symmetrical broadband characteristics. In the co-pending application of Ross L. Bell, one of the inventors hereof, now Patent No. 3,134,979 issued May 26, 1964 there is disclosed a novel logarithmic antenna of the trapezoidal type employing folded dipole radiators of broadband characteristics.

It is a principal object of this invention to provide a novel antenna of the log-periodic type which is of simple construction and has highly desirable structural features, i.e. one which is of relatively light weight, rugged, and can withstand large wind loading, and which may be used for space radiation or may be imaged over the ground or counterpoise, resulting in such case in a substantial reduction in the antenna height for the same range of operating frequency.

Another objects of the present invention is to provide a novel logarithmic periodic antenna employing triangular antenna elements instead of trapezoidal elements as used in the earlier application, together with attending structural advantages not possible heretofore in the art.

A feature of the present invention is to provide a novel, simply constructed, broadband log-periodic antenna that comprises, in eifect, a series of dipole radiators that diverge from an apex to form triangular tooth antenna elements and in which the pertinent dimensions of the radiators increase uniformly and proportionally with an increase in distance from the apex of the structure, the said dipole radiators being supported at their apexes from a catenary cable and energized at their bases from a feed line.

A feature of the present invention is to provide a novel antenna of the above character that is so structurally arraged as to be shipped in folded condition and unwrapped at the site of use to enable the same to be easily, quickly and accurately installed in the field and which is foolproof, of low maintenance cost, and which is especially well designed to withstand high Wind and ice loads.

Another feature of the present invention is to provide a novel antenna of the above character employing novel simply constructed supporting means for the triangular tooth-like antenna elements together with quickly assembled fittings for accurately positioning the various antenna elements when installing the same.

Another feature of the present invention is to provide a novel vertically polarized broadband antenna providing unidirectional coverage and employing rod or wire elements in triangular form and which is capable of long haul, point-to-point communication use, the radiation pattern and operating impedance of the antenna being substantially constant over the operating range.

Another feature of the present invention is to provide an antenna of the above character wherein energy from the antenna terminals when acting as a transmitter travels along a wire transmission line toward the large or rear end of the structure until it reaches the active region, that being the one in which the dipole elements that are near resonance wavelength at the operating frequency.

Still another feature of the present invention is to provide a novel antenna that is well adapted to be used as a monopole array operating in conjunction with the ground or a counterpoise and capable of providing radiating energy moving outwardly from the apex of the antenna at very low angles with respect to the horizon.

Another feature of the present invention is to provide a novel and simple arrangement for furnishing energy to to dipole elements by means of a wire transmission line and couplings by which means energy is capacitively coupled to the dipole elements in a shunt feed arrangement.

These and other features and advantages of the present invention will be more apparent after a perusal of the following specification taken in connection with the accompanying drawings wherein,

FIG. 1 is a view of the side elevation of the novel antenna structure of this invention employed as a monopole array.

FIG. 2 is an enlarged fragmentary view of a portion of the structure of FIG. 1 encompassed in a circle 2-2 of FIG. 1.

FIG. 3 is an enlarged fragmentary view taken along lines 3-3 of FIG. 1 looking in the direction of the arrows.

FIG. 4 is enlarged section and end elevational views of the structure encompassed by the circle 4-4 of FIG. 1.

FIG. 5 is an enlarged fragmentary view taken along lines 5-5 and looking in the direction of the arrows of FIG. 1.

FIG. 6 is an enlarged view taken along line 6-6 of FIG. 1 and looking in the direction of the arrows with parts broken away.

FIG. 7 is a fragmentary view taken along lines 7-7 of FIG. 5 with parts broken away.

FIG. 8 is a plan view of a novel ground screen adapted to be used with the antenna of this invention.

FIG. 9 is an enlarged detail view of the structure encompassed by circle 9-9 of FIG. 8.

FIG. 10 is an enlarged fragmentary view encompassed by circle 10-10 of FIG. 8.

FIG. 11 is an enlarged fragmentary view encompassed by circle 11-11 of FIG. 8.

FIG. 12 is an enlarged fragmentary view encompassed by circle 12-12 of FIG. 8.

FIG. 13 is an enlarged fragmentary view encompassed by circle 13-13 of FIG. 8.

FIG. 14 is an enlarged fragmentary view encompassed by circle 14-14 of FIG. 8.

FIG. 15 is an enlarged fragmentary view encompassed by circle 15-15 of FIG. 8.

Similar characters of reference are used in the above figures to designate corresponding parts.

Referring now to the drawings, the novel logarithmic periodic antenna of this invention comprises a series of mutually spaced substantially triangular radiator teeth or arrays, each comprising dipole elements or radiators 1, 2 which are interconnected at their upper ends form- 1ng an apex and supported from a catenary cable 3- by brackets 4, 5 and vertical cables 6. The arrays 1, 2-1, 2 are arranged in a plane and are shown imaged over ground as by use of a ground screen or counterpoise 9. The dimensions of the radiators 1, 2-1, 2 and their spacing increase uniformly and proportionally with the increase in distance from the apex of the structure.

The catenary cable 3 and the cables 6 are preferably of insulated material such as glass fiber or epoxy fiberglass, the cable 3 being shown made up in sections interconnected by brackets 7. The rear end of the cable 3 is attached to and carried by the upper end of an antenna tower 8, where as the forward end of this catenary is supported by a post 19 adjacent the apex of the array, both the tower 8 and post 19 being firmly anchored to the ground so as to keep the cable 3 under tension desired value by use of a tension indicator (see FIG. 3) connected through turnbuckle 33 to the upper portion of post 19, thereby maintaining the arrays 1, 21, 2 under proper tension in use.

The arrays 1, 21, 2 are capacity coupled to a feed line 11 that is positioned slightly above the ground plane adjacent the antenna apex. This feed line 11 is inclined upwardly from the ground plane looking toward the rear of the array, so that the height of this feed line above the ground plane 9 increases progressively with distance from the apex. The feed line 11, preferably a reinforced copper cable covered with insulation 17, extends parallel to a similar cable 14, which latter cable is cut adjacent the antenna teeth dipole elements 1 and 2 as particularly shown in FIG. 6. Alternate end portions of the cut cable 14 adjacent each of the elements 1 and 2 are bent outwardly forming stubs or pigtails 15 and 15 which are electrically connected by clamps 16 to dipole elements 1 and 2 respectively of the radiator antenna teeth.

The portions 14' of the lead 14 interconnecting the leads 1 and 2 of the respective radiator teeth extend along the feed line 11 though insulated therefrom by low loss dielectric 17 such as clear polyethylene and spaced sufficiently from the feed line to obtain the optimum impedance match therebetween. The thusly insulated leads 11 and 14 are additionally provided with an external thin sheath, as of black polyethylene 18, which is thickened at 18' in the region of pigtails 15 to provide good weather resistance to the insulated cables 11 and 14. The weather resistant coating 18 is also used to cover the clear polyethylene insulation filling the gaps between the stubs 15 and the cut ends of lead 14. The portions of cable 14 extending between the antenna teeth do not carry current in use.

Thus, it will be seen that the portions 14' of cable 14 act as distributed capacitors for capacity coupling the respective dipole elements 1 and 2 of the antenna teeth to the feed line 11. The mutual spacing of the respective teeth of the antenna enables the feed line 11, acting together with the distributed capacitors 14', to provide suflicient phase shift between the dipole elements of the respective antenna teeth to enable the antenna to serve as a backfire radiator, so that the directional lobe from the antenna when acting as a transmitter extends outwardly from the apex of the antenna in the direction of the axis thereof and toward the left as viewed in FIG. 2.

In FIG. 2, the feed line 11 is shown supported at the apex end of the antenna through a turnbuckle 29 to the post 19 whereas this feed line is supported at the rear end of the antenna through a turnbuckle 20' to a rod of the antenna tower 8. The feed line 11.is additionally grounded on the tower 8 by jumper 34.

The high tension output of an input transformer 21 is shown connected by lead 22 (see FIG. 2) to feed line 11 whereas the low tension output of this transformer is connected to the ground plane 9.

The ground plane 9 is provided with a central longeron 12 extending just above the ground and beneath the antenna teeth, which longeron may be a rigid pipe supported as on blocks 24. The longeron 12 is provided at the factory with bolt holes for receiving bolts 23 (see F IG. 4) properly located therealong to which the re- "spective lower ends of Wires or rods 1 and 2 are connected. Jumpers 25 received by C-clamps 26 serve to 7 ground the lower ends of rods 1 and 2 on the wires .27

of the counterpoise 9.

As especially shown in FIG. 8, the ground plane 9 comprises diagonally crossing mutually spaced wires 13 and 27 that cross the longeron 12 at the point-s where bolts 23 attach the lower ends of rods 1 and-2 to the longeron. Thus, as shown in FIG. 10, the crossing wires 13 and 27 are shown connected by jumpers 25 and 25 ,and bolts 23 to the longeron jumper 25 also being connected to an antenna rod 1 for example. The outer ends of the diagonal wires 13, 27 are grounded by suitable ground pegs. A wire 29 extends transversely of the array at post 19 and is attached, as shown in FIGS. 9, l2 and 14, to the ground screen wires 13 and 27 as by use of crimped C-clamps 32, and at appropriate points ground pegs 3-5 are used to anchor and ground the wires. The wires 13 and 27 extend forwardly from transverse wire 29 to another transverse wire 30 positioned forwardly of post 19 and are fastened to this wire and to ground, as illustrated in FIG. 15.

FIG. 11 illustrates the manner of attaching the ground wires 13 and 27 to the antenna tower S by use of jumper-s.

The thusly constructed antenna and ground screen can be easily and rapidly installed in the field Without the possibility of error since all dimensions are fixed at the factory, and the antenna can be largely rolled up at the factory with the exception of the longeron 12 and shipped so rolled and then unwrapped on the site of use. No dimensional adjustments in the field are required with the setting of the oatenary tension at the prescribed value by means of the tension indicator 10 provided with the array. The use of the triangular configuration instead of the trapezoidal con-figuration of the earlier application, now Patent No. 3,134,979, results in a number of advantages, namely, for the equivalent number of radiator teeth, one-half the number of dielectric drop suspension lines 6 are required compared to the structure of the earlier fi-led application. The triangular teeth array is much easier to erect in practice and to maintain at desired tension without the need of adjustment of the individual radiator tension.

Prefabricated longeron pipe 12 with its connected bolts 23 for holding down the antenna rods 1 and 2 provides for accurate location of these rods to obtain the most efficient operation. The rods 1 and 2 can be provided with offset portions for receiving the clamps 16 holding the feed wire 11 in the desired vertical position with respect to the rods 1 and 2, so that this feed wire and distributive capacity members or coupling sections 14' incline upwardly from the apex of the antenna at the desired optimum angle to obtain the best operating results in practice. The dimensions of the monopole elements, their spacing and the length of the, coupling sections are such as to furnish an energy transfer between the transmission line and the monopole elements with a phasing and amplitude which enhances the directivity of the radiation from the structure. The rugged, simple construction of the antenna array providing for simplicity in feeding the tooth elements with energy, ruggedness of construction, the elimination of the need for adjustment in the field, relatively light weight, and large power handling capability, renders the antenna highly practical and desirable in use.

Since many changes could be made in the above construction of the novel logarithmic periodic antenna of this invention and many apparently widely different embodiments of this invention could'bemade without departing from the scope thereof, it is intended'that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. For example, the distributed capacitors 14' could be replaced, if desired, by lumped capacitors connecting the feed line 11 to each of the rods or wires 1 and 2 of the antenna tooth structures.

What is claimed is:

-1. A directional logarithmic periodic antenna having an apex adjacent the ground and comprising a series of mutually spaced triangular hollow tooth structures lying in a common vertical plane and disposed at progressively greater distances from said antenna apex, a catenary cable for supporting the upper ends of said tooth structures, each of said tooth structures comprising a pair of oppositely inclined rods forming an apex at their upper ends supported from said catenary, the dimensions of the tooth structures progressively increasing with distance from the antenna apex, a feed line extending alongside said tooth structures from said antenna apex, the height of said feed line above ground progressively increasing toward the rear of said antenna, distributive capacity members successively disposed alongside said feed line, each of said capacity members comprising a conductor having its ends respectively connected to the rods of a respective one of said tooth structures for capacity coupling said feed line to said tooth structures, a longeron extending along the ground beneath said triangular tooth structures and having the rods of said structures attached thereto at predetermined points, and a ground screen underlying said antenna having diagonal wires crossing said longeron and connected thereto at the points of connection of the triangular tooth structu-re rods thereto, the free ends of said diagonal wires being grounded.

2. A log periodic antenna comprising a series of hollow triangular tooth arrays extending from an apex and being mutually spaced in increasing distances from each other, said arrays having wire or rod sides, the bottoms of said triangular tooth arrays being defined by a feed line extending from the apex of the array rearwardly and upwardly uniformly, said arrays also being of progressively larger dimensions and lying in a vertical plane, means for supporting said triangular tooth arrays comprising a post adjacent the apex of the array and a tower at the rear thereof, a catenary cable extending between said post and tower, tensioning means for maintaining said cable at a desired tension, suspension cables connecting the apexes of said triangular tooth arrays to said catenary cable, said feed line being supported from said post and from said tower and capacitively coupled to the inclined rods or wires of said arrays for interchanging energy therewith, a rigid longeron extending the length of the antenna just above ground, said longeron being connected to the respective rods or wires of the tooth arrays at predetermined points, a countenpoise extending beneath said arrays, comprising diagonally extending mutually spaced wires that cross each other at the longeron and are connected thereto at the same points as said triangular tooth arrays, said wires being grounded, and plurality of longitudinally extending wires connected to said diagonal wires at their forward ends, said longitudinally extending wires projecting in front of said antenna and being grounded.

References Cited by the Examiner UNITED STATES PATENTS 2,989,749 6/1961 -Du Hamel et a1. 343908 X 3,079,602 -2/ 1963 Du Hamel et al. 343-792.5 3,101,474 8/ 196-3 Wickersham et al. 343792.5 3,123,827 3/1964 Arnold et al. 343-7 92.5 3,165,748 1/1965 Woloszczuk 343-792.5 3,179,943 4/1965 Buzbee 343--792.5 3,212,094 10/ 19-65 Berry 343792.5

HERMAN KARL SAALBACH, Primary Examiner.

E. LIEBERMAN, Assistant Examiner. 

1. A DIRECTIONAL LOGARITHMIC PERIODIC ANTENNA HAVING AN APEX AJDACENT THE GROUND AND COMPRISING A SERIES OF MUTUALLY SPACED TRIANGULAR HOLLOW TOOTH STRUCTURES LYING IN A COMMON VERTICAL PLANE AND DISPOSED AT PROGRESSIVELY GREATER DISCTANCES FROM SAID ANTENNA APEX, A CATENARY CABLE FOR SUPPORTING THE UPPER ENDS OF SAID TOOTH STRUCTURES, EACH OF SAID TOOTH STRUCTURES COMPRISING A PAIR OF OPPOSITELY INCLINED RODS FORMING AN APEX AT THEIR UPPER ENDS SUPPORTED FROM SAID CATENARY, THE DIMENSIONS OF THE TOOTH STRUCTURES PROGRESSIVELY INCREASING WITH DISTANCE FROM THE ANTENNA APEX, A FEED LINE EXTENDING ALONGSIDE SAID TOOTH STRUCTURES FROM SAID ANTENNA APEX, THE HEIGHT OF SAID FEED LINE ABOVE GROUND PROGRESSIVELY INCREASING TOWARD THE REAR OF SAID ANTENNA, DISTRIBUTIVE CAPACITY MEMBERS SUCCESSIVELY DISPOSED ALONGSIDE SAID FEED LINE, EACH OF SAID CAPACITY MEMBERS COMPRISING A CONDUCTOR HAVING ITS ENDS 